The Trackline Report (SPR) communicates a search pattern from the mission controller to a SRU (either to transmit a pattern for action or to cancel a pattern) or from a SRU to the MC (reporting acceptance or completion).
Summary of changes:
Version 0:
This is an RTCM compliant update of the FID 3 message listed in the Oct 2014 EAIS IDD. The FID was changed to avoid confusion with previously published message definitions.
There are AIS Message 25 and 8 variants of this message, but the encrypted message 8 is not implemented.
Encrypted Trackline Report Segment 1 (Message 26, Broadcast)
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Parameter |
# of Bits |
Description |
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Standard Message Header |
Message ID |
6 |
Identifier for Message 26; always 26. |
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Repeat Indicator |
2 |
Indicates how many times a message has been repeated. 0 – 3; 0 = default; 3 = do not repeat any more. Set to zero (default). |
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Source MMSI |
30 |
MMSI number of source station. Varies according to the transmitter ID. |
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Destination Indicator |
1 |
0 = Broadcast (no Destination ID field used) 1 = Addressed (Destination ID uses 30 data bits for MMSI) Set to 0, broadcast. |
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Binary Data Flag |
1 |
0 = unstructured binary data (no Application Identifier bits used); 1 = binary data coded as defined by using the16-bit Application identifier. Set to 1, structured. |
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Binary Data |
Designated Area Code |
10 |
Designated area code (DAC). This code is based on the maritime identification digits (MID). Set to 366. |
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Function Identifier |
6 |
Function identifier. Set to 15. |
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Encrypted Payload |
Version |
3 |
Sequential number used to indicate the message version in steps of 1. 0 = test message = default; 1 – 7 = message version. Set to zero. |
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Message Linkage ID |
10 |
Identifier for the SAR Pattern Report. This number uniquely identifies a search pattern sent from a given SMC (MMSI) and is used to connect additional information with the search. Source MMSI and this ID uniquely identify the event. Set to 1 - 1023 by message originator; 0 = not available. |
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Message Segment |
5 |
Number of this message segment; sequential number. Recipient will need to receive all segments and put in order sequentially. 0 – 31. Set to 0. |
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Number of Segments |
5 |
Total number of segments comprising the complete Trackline Report (Total = N+1). N = 0- 31. |
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Pattern Type |
2 |
Type of search pattern: 0 = Trackline Search Pattern or route = default; 1 = Polygon; 2-3 = reserved. |
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Encrypted Payload |
Search Pattern Status |
3 |
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Reference Time |
UTC Day |
5 |
UTC Day 1 – 31; 0 = UTC day not available = default. |
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UTC Hour |
5 |
UTC Hour. 0 – 23; 24 = UTC hour not available = default; 25 - 31 = reserved. |
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UTC Min |
6 |
UTC Minute. 0 – 59; 60 = UTC minute not available = default; 61 - 63 (reserved for future use). |
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Action SRU MMSI |
30 |
MMSI of the Action SRU. This varies according to the MMSI of the desired unit. 0 = unknown = default; |
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Case ID Number |
30 |
Case ID. Maximum 5 characters 6-bit ASCII as defined in ITU 1371-5, Table 47. “@@@@@” = not available = default. If less than 5 characters, the remainder of the parameter should be filled with “@” characters (set bits to 0); but, not shown on the presentation. |
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Search Point |
Longitude |
28 |
Longitude in 1/10,000 minute. (±180°) East = positive (as per 2’s complement); West = negative (as per 2’s complement); 181° = not available = default. |
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Latitude |
27 |
Latitude in 1/10,000 minute (±90°) North = positive (as per 2’s complement); South = negative (as per 2’s complement); 91° = not available = default. |
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Search Altitude |
7 |
Altitude for search pattern in 50 ft increments. 0 = sea level; 50 – 6000 ft; 121 = not specified = default; 122 – 127 = reserved. |
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Search Speed |
9 |
Speed to execute the search pattern in 1kt increments. 0 = not specified = default; 1 – 500 kts; 501 – 510 = reserved; 511 – not to be used. |
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Encryption Bit Padding |
81 |
Sufficient spare bits to ensure that the binary data is a multiple of 128 bits for block encryption (256). Set to 0. |
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Checksum |
16 |
16-bit CRC calculated as per EAIS Specification |
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Footer |
Spare |
4 |
Four extra bits added to ensure the message ends on a byte boundary. Set to zero. |
Communications State Selector |
1 |
0 = SOTDMA communication state follows, 1 = ITDMA communication state follows |
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Communications State |
19 |
SOTDMA communication state (see ITU 1371-5 § 3.3.7.2.1, Annex 2), if communication state selector flag is set to 0, or ITDMA communication state (§ 3.3.7.3.2, Annex 2), if communication state selector flag is set to 1. |
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Total bits |
352 |
2 Slot Binary Message |
Encrypted Trackline Report Segment 2-32 (Message 26, Broadcast)
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Parameter |
# of Bits |
Description |
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Standard Message Header |
Message ID |
6 |
Identifier for Message 26; always 26. |
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Repeat Indicator |
2 |
Indicates how many times a message has been repeated. 0 – 3; 0 = default; 3 = do not repeat any more. Set to zero (default). |
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Source MMSI |
30 |
MMSI number of source station. Varies according to the transmitter ID. |
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Destination Indicator |
1 |
0 = Broadcast (no Destination ID field used), 1 = Addressed (Destination ID uses 30 data bits for MMSI) Set to 0, broadcast. |
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Binary Data Flag |
1 |
0 = unstructured binary data (no Application Identifier bits used); 1 = binary data coded as defined by using the16-bit Application identifier. Set to 1, structured. |
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Binary Data |
Designated Area Code |
10 |
Designated area code (DAC). This code is based on the maritime identification digits (MID). Set to 366. |
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Function Identifier |
6 |
Function identifier. Set to 15. |
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Encrypted Payload |
Version |
3 |
Sequential number used to indicate the message version in steps of 1. 0 = test message = default; 1 – 7 = message version. Set to zero. |
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Message Linkage ID |
10 |
Identifier for the SAR Pattern Report. This number uniquely identifies a search pattern sent from a given SMC (MMSI) and is used to connect additional information with the search. Source MMSI and this ID uniquely identify the event. Set to 1 - 1023 by message originator; 0 = not available. |
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Message Segment |
5 |
Number of this message segment; sequential number. Recipient will need to receive all segments and put in order sequentially. 1 – 31. |
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Number of Segments |
5 |
Total number of segments comprising the complete Trackline Report (Total = N+1). N = 0- 31. |
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Search Point |
Longitude |
28 |
Longitude in 1/10,000 minute. (±180°) East = positive (as per 2’s complement); West = negative (as per 2’s complement); 181° = not available = default. |
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Latitude |
27 |
Latitude in 1/10,000 minute (±90°) North = positive (as per 2’s complement); South = negative (as per 2’s complement); 91° = not available = default. |
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Search Altitude |
7 |
Altitude for search pattern in 50 ft increments. 0 = sea level; 50 – 6000 ft; 121 = not specified = default; 122 – 127 = reserved. |
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Search Speed |
9 |
Speed to execute the search pattern in 1kt increments. 0 = not specified = default; 1 – 500 kts; 501 – 510 = reserved; 511 – not to be used. |
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Encryption Bit Padding |
34 |
Sufficient spare bits to ensure that the binary data is a multiple of 128 bits for block encryption (128). Set to 0. |
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Checksum |
16 |
16-bit CRC calculated as per EAIS Specification |
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Footer |
Spare |
4 |
Four extra bits added to ensure the message ends on a byte boundary. Set to zero. |
Communications State Selector |
1 |
0 = SOTDMA communication state follows 1 = ITDMA communication state follows |
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Communications State |
19 |
SOTDMA communication state (see ITU 1371-5 § 3.3.7.2.1, Annex 2), if communication state selector flag is set to 0, or ITDMA communication state (§ 3.3.7.3.2, Annex 2), if communication state selector flag is set to 1. |
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Total bits |
224 |
2 Slot Binary Message |